Broadcast systems typically comprise at least three types of system. Traffic systems schedule advertising, programming systems schedules programming, and an automation system broadcasts or plays the combination from traffic and programming systems based on a broadcast, or format, clock. The clock provides a template for programming which includes top of the hour station IDs, commercial breaks, news breaks, talk breaks, and other programming. An automation system operates from merged logs (called “live logs” or “final logs”) of the traffic and programming systems to create main program audio for broadcast. In many cases, the automation system is the main play out system. The automation system audio path may lead to mixers, switches, consoles, and eventually to a broadcast audio processing chain, which may also include a studio-to-transmitter link (STL).
A play out system is a system that can play content for broadcast. If a secondary play out system is used such that for example to insert real time program content, the primary play out system must signal, or trigger, the secondary system to begin playing program content, for example ads. There exists a need for a robust method for signaling these events.